The present invention relates to a protective circuit device for a storage battery for preventing overcharge to the storage battery, circuit board device of the protective circuit, and storage battery pack provided with the protective circuit device.
In electronic devices such as portable telephones, a storage battery pack with a storage battery enclosed in a resin casing is generally used as a power supply source. In most cases, a protective circuit device for preventing overcharge to the storage battery is included in the storage battery pack. The protective circuit device has a charging terminal for charging the storage battery with electricity from a domestic plug socket or the like, and a discharging terminal for supplying electricity to a terminal device such as a portable telephone. An exemplary conventional protective circuit device is shown in FIGS. 12 and 13.
A protective circuit device 3 shown in FIGS. 12 and 13 has a prescribed interconnection pattern (not shown) and a circuit board 32 on which various electronic parts 6, including a chip resistor, are mounted. Circuit board 32 is in an L shape, and has metal terminals 40 and 41 at both ends. In addition, a first terminal portion 32C and a second terminal portion 34A, in which a plurality of metal pieces are inserted into resin, are mounted to protective circuit device 3. Terminal portions 32C and 34A are electrically connected to metal terminals 40 and 41.
First terminal portion 32C has a structure in which the region of the metal piece is partially exposed from the surface of a resin portion 32c. First terminal portion 32C is mounted to circuit board 32 such that the exposed region is on the side of the back surface of circuit board 32 (faces down). The exposed region turns to, for example, charging terminal 31. On the other hand, second terminal portion 34A has a structure in which each metal piece is partially exposed from the upper surface of a so-called terminal base 34B (a resin portion) having a prescribed height. The region in which the metal piece is exposed turns to, for example, discharging terminal 30.
Terminal base 34B has a horizontal portion 34a in which the metal terminal is exposed, as well as a vertical wall 34c and a plurality of leg portions 34b that are downwardly extending from horizontal portion 34a. Namely, with second terminal portion 34A mounted to circuit board 32, a prescribed space is formed between circuit board 32 and the lower surface of horizontal portion 34a, as shown in FIG. 13. Thus, various electronic parts 6 can be mounted in the region of circuit board 32 directly below horizontal portion 34a before mounting second terminal portion 34A. After mounting electronic parts 6, second terminal portion 34A is mounted to circuit board 32 such that contact between second terminal portion 34A and electronic parts 6 is avoided.
However, the above described protective circuit device 3 suffers from problems related to a low efficiency in manufacture and cost involved. The reason is as follows. Since first and second terminal portions 32C and 34A are formed by inserting metal pieces into resin, steps of forming terminal portions 32C and 34A are additionally required. Further, in the steps of forming terminal portions 32C and 34A, molds for forming resin portions 32c and 34B of terminal portions 32C and 34A and for inserting the metal pieces are required. The molds are required for each of terminal portions 32C and 34A.
Moreover, manufactured protective circuit device 3 should be tested to determine as to if it operates as designed. Then, if protective circuit device 3 is determined to be defective due to a mounting failure of electronic part 6 mounted in a region of circuit board 3 corresponding to second terminal portion 34A, such poorly mounted electronic part 6 cannot be re-mounted unless second terminal portion 34A is removed. Thus, if electronic part 6 is not properly mounted in the region of circuit board 32 corresponding to second terminal portion 34A, protective circuit device 3 must be discarded, whereby the yield is decreased.
The present invention is made to solve the aforementioned problems. An object of the present invention is to manufacture a protective circuit device and storage battery pack with high efficiency and favorable cost.
A circuit board of a protective circuit for a storage battery according to the present invention has a first board including a circuit portion, and a second board connected to the first board through a deformable conductive member. The circuit portion includes, for example, an interconnection pattern and an electronic part connected thereto. The conductive material may be a metal piece, for example.
The first board preferably has a first external terminal electrically connected to the circuit portion. The second board preferably has a second external terminal electrically connected to the circuit portion.
Further, the first board preferably has a protrusion protruding from one end thereof. In this case, the first external terminal is formed on the protrusion. The second board is preferably arranged on the side opposite to the protrusion with respect to and spaced from the first board.
A third board may be provided between the first and second boards. In this case, the first, second, and third boards may be connected by the same conductive member. The conductive member may include the first and second conductive members. Then, the first conductive member connects the first and third boards, whereas the second conductive member connects the second and third boards.
Further, the first and second boards may be formed in the region surrounded by a frame. A plurality of such regions are provided, each having the first and second boards.
Normally, various electronic parts and the like are mounted on the board with a plurality of boards collectively connected by the frame. After terminals to be electrically connected to the mounted electronic parts are formed, each board is separated from the frame. Thus, a circuit for an intended use is obtained. Here, as the second board (island) is connected to the first board (the circuit board body) through the conductive member, the second and the first boards are maintained in a desired positional relationship with the conductive member bent. For example, the second board can be vertical or parallel to the first board. In addition, if the circuit board of the protective circuit has a third board (island), for example, the second board can be parallel to the first board and the third board can be vertical to the first board thereby connecting the first and second boards.
Since the second board is connected to the first board through the conductive member, the second and first boards can be electrically connected. In this case, the second board may be provided with electronic parts and terminals. If the protective circuit board is provided with a third board, the second board can be parallel to the first board by separating the board from the frame and bending the conductive member. Thus, if the external terminal is formed on the second board, for example, the above mentioned second and third boards serve as the second terminal portion of the conventional example.
If the second board is parallel to the first board and the second board is arranged directly above the first board, a prescribed space is obtained between the first and second boards. The height of the space can be determined by appropriately selecting the dimension of the third board, length of the conductive member and the like. Various electronic parts are mounted to the first board before bending the conductive member, for example in the state of collective board. In this case, by appropriately setting the height of the space, contact between the second board and the electronic parts can be avoided even if the second board is arranged directly above the first board after the electronic parts are mounted. In addition, at least the thickness of the storage battery ensures the thickness of the protective circuit device (a distance between the second and first boards). Accordingly, the electronic parts can also be mounted on opposing surfaces of the first and second boards, whereby the mounting area of the electronic parts can be increased.
The circuit board of each protective circuit can be tested as to if it operates as intended in the state of the collective board with the protective circuit board supported by the frame. Since the test is performed with the second terminal portion formed, if the electronic parts are not properly mounted below the horizontal portion of the second terminal portion, it is difficult to re-mount the electronic parts. On the other hand, in the present invention, test is performed with the first and second boards being flush with each other in the state of the collective board, i.e., with the electronic parts being mounted. Thus, if the test reveals that the electronic part is poorly mounted, such an electronic part can easily be re-mounted, so that the yield increases. Further, as the first and second external terminals are respectively formed on the first and second boards in the state of collective board, an amount of displacement in position between the external terminals after the manufacture of the protective circuit device can be reduced as compared with the conventional example where the external terminal portion is separately mounted to the board.
A protective circuit device for a storage battery according to the present invention includes a first board having a circuit portion, and a board connected to the first board through a conductive member.
The first board preferably has a first external terminal electrically connected to the circuit portion, and the second board preferably has a second external terminal electrically connected to the circuit portion.
The conductive member is preferably bent, and the second board is arranged opposite to and spaced from the first board.
The first board may have a protrusion. In this case, the first external terminal is formed on the protrusion. The second board is connected to the end of the first board positioned on the side opposite to the protrusion.
Electronic parts electrically connected to the circuit portion may be mounted on the surface of the second board that is opposite to the first board.
Further, a third board may be provided between the second and first boards. In this case, the third board may be vertical to the first board and may have an interconnection pattern electrically connected to the circuit portion on the surface of the third board.
An electronic part without a coating for increasing moisture resistance may be mounted on the second board, and that with such a coating may be mounted on the first board.
According to the protective circuit device for a storage battery of the present invention, the second board can be vertical to or parallel to the first board by bending the conductive member. Thus, the protective circuit device can be conveniently incorporated in the storage battery pack.
Some protective circuit devices are coated with epoxy or acrylic based resin, and the like. Although the coating operation is performed on a specific electronic part, in this case, the electronic parts not to be coated should be masked with a polyimide tape or the like. In the protective circuit device of the present invention, the first and second boards are connected through the conductive member, but the mounting surfaces of the electronic parts of the boards are separated. Thus, the electronic parts without coatings are concentrated on the second board, and those with coatings are concentrated on the first board, so that the coating operation can be intensively performed on the first board. As a result, the electronic parts not to be coated, i.e., those mounted to the second board, needs not be masked. Thus, in the protective circuit of the present invention, an operation of coating the electronic parts with resin is not only facilitated, but a masking operation for coating can advantageously be eliminated.
In addition, when the third board is provided, the second board is parallel to the first board, and the third board is vertically connected to the first and second boards, a terminal base of the conventional protective circuit device can be formed by the second and third board. Here, formation of the external terminal on the second board enables formation of a portion corresponding to the conventional second terminal portion by the second and third board as well as the external terminal. Thus, the second terminal portion needs not be separately formed by insertion, so that manufacturing efficiency of the protective circuit device is increased and cost is reduced.
A protective circuit device according to the present invention can be obtained by directly forming the external terminal on the protective circuit board in the state of collective board, for example, and by bending the conductive member after separating the protective circuit board from the collective board. A series of the above described operations enables formation of the portion corresponding to the second terminal portion of the conventional protective circuit device. Accordingly, there is no need to mount the second terminal portion to the first board. In addition, since the portion corresponding to the second terminal portion needs not be formed by resin molding, there is no need to prepare a mold. Thus, cost involved is extremely favorable.
In addition, a plurality of external terminals to be electrically connected to the interconnection pattern can be directly formed. Namely, the portion corresponding to the first terminal portion of the conventional protective circuit device can directly be formed in the first board. In this case also, manufacturing efficiency of the protective circuit device is increased and cost is reduced. Although the first terminal portion is also formed by insertion as in the case of the second terminal portion, which is in turn mounted to the protective circuit board such an operation is not necessary in the convention protective circuit device.
It is noted that each external terminal portion may be formed by mounting a terminal such as metal, or by coating a terminal pad, which is formed simultaneously with the interconnection pattern, with metal.
A storage battery pack of the present invention includes a storage battery, a protective circuit device electrically connected to the storage battery to prevent overcharge to the storage battery, and an insulation casing enclosing the storage battery and the protective circuit device. The protective circuit device includes a first board having a circuit portion, and a second board connected to the first board through a conductive member.
The conductive member is preferably bent. At the time, the second board is preferably arranged in a position opposite to and spaced from the first board. The second board has a second external terminal electrically connected to the circuit portion. The first board preferably has a first external terminal electrically connected to the circuit portion. The first and second external terminals are exposed from the surface of the insulation casing.
A storage battery may be inserted between the second and first boards.
The storage battery pack of the present invention is provided with the above described protective circuit device, so that aforementioned various effects are produced. Therefore, the storage battery pack of high performance can be provided with low cost.